1. Field of the invention
The invention relates to a station for continuous unwinding of a material web, notably a paper or cardboard web.
2. Description of the related art
Unwinding stations for continuous unwinding of a material web are previously known. They serve the continuous unwinding of a material web from a reel and precede a machine for converting the material web, for example, a coater. A known unwinding station includes a primary and a secondary unwinding system serving to carry a reel. A full reel, to begin with, is carried by the primary unwinding system while the material web unwinds. Once the reel has reached a desired diameter, it is transferred from the primary to the secondary unwinding system. Employed for that purpose are pivoting arms which pivot about an axle and engage the reel on its two ends, transferring it in a pivotal movement to the secondary unwinding system. Next, the primary unwinding system receives a new, full reel, and the material web wound on it is spliced to the material web unwinding from the reel carried by the secondary unwinding system before it is unwound entirely. Provided for that purpose is a splicing system featuring a splicing roll that pivots about an axle and carries the material web unwinding from the reel to the material web converting machine. The reel is carried by the secondary unwinding system. To splice the two material webs together, the splicing roll pivots to press onto the reel carried by the primary unwinding system. Simultaneously with it, the material web which is unwinding from the reel carried by the secondary unwinding system is separated by use of a cutting device.
The known unwinding station has the disadvantage of having to exert, due to the heavy weight of the reel, very large forces in order to pivot this load in the transfer from the primary to the secondary unwinding system. The weight of the reel may amount to up to 40 tons. Required therefor are several separate hydraulic cylinders which pivot the arms, and which are very expensive and rugged in design. A further drawback is that the dimensions of the unwinding station, i.e., its vertical and longitudinal expanse, are relatively large on account of the great space needs of the pivoting construction, which serves to transfer the reel or position the splicing system. The costs of the unwinding station are high, specifically due to the pivoting constructions.
The present invention provides an unwinding station which features a simple and compact structure and allows a reliable use.
An unwinding station is distinguished by an auxiliary drive with the aid of which a torque can be exerted onto the reel while it transfers from the primary to the secondary unwinding system. Moving jointly with the reel, the auxiliary drive makes it possible to hold or adjust the unwinding traction of the material web unwinding from the reel to a desired value, notably during the transfer of the reel. As a result, the splice between the two material webs can be passed safely through the converting machine following the unwinding station.
An advantage of the present invention is that the reel can be moved along a first straight line which extends parallel to an imaginary horizontal line. An expensive pivoting construction and the hydraulic cylinders producing the pivotal movement, such as used with the known unwinding station, are thus dispensable, allowing a simplification of the structure of the unwinding station and a reduction of its overall height and/or length. Additionally, it is possible to also use the auxiliary drive while the reel is carried by the primary or the secondary unwinding system. Hence, the primary and the secondary unwinding systems are arranged at an equal level, i.e., at a same height, allowing a transfer of the reel with relatively low forces. The horizontal arrangement of the unwinding station makes it possible to simplify the design of the carrying system.
The splicing system features at least one splicing roll which, by use of a linear guide system, can be moved along a second straight line. This design allows simplifying the structure of the unwinding station. Furthermore, little space is needed for the linear guide system, which makes it possible to reduce both the length and height of the unwinding station.